"Multi-Agent" Is Often a Single Agent: What 86 Repos Actually Implement

Every agent framework README says "multi-agent". AutoGen, CrewAI, LangGraph, MetaGPT each have 20k+ GitHub stars, and the term "multi-agent" appears in thousands of repo descriptions. But what do projects that call themselves multi-agent actually implement? Until now, nobody measured the population — only how to build frameworks, or theory about whether multi-agent is "just prompting". A new census (86 strictly-filtered, self-described "multi-agent" repos with 1k+ stars, plus 18 seed frameworks, snapshot-pinned) annotates a three-axis taxonomy to full-population ground truth: (i) model-instance structure, (ii) topology, (iii) judge/critic presence. The headline: the label-reality gap 68.2% of self-described multi-agent repos (58/85, Wilson 95% CI [57.7%, 77.2%]) are single-model or non-agent systems. "Multi-agent" overclaims what is implemented. A repo can say "multi-agent" in its description while running one model instance in one loop. Among the 27 genuine multi-agent systems: Orchestrator-worker is the plurality topology — 48.1% (13/27, CI [30.7%, 66.0%]) — coordinator + workers, not peer teams. Judge/critic agents are rare — 1 of 30 annotated repos (3.3%). For all the talk about critic/reviewer agents, almost nobody implements them. There's also a reverse gap: monorepo-aware manifest extraction found 44 repos with framework dependencies — including repos that use multi-agent frameworks (langroid, lumibot, wigolo...) without claiming the label. The gap runs both directions. Why the census matters (and its honest limits) The classifier went through three documented generations: v1 degenerate, v2 framework-API (81.2% full-population), v3 README-role (100.0% in-sample, mechanistic rules, no repo-name hardcoding). Framework-API detection systematically misses the 11 framework-free hand-built MAS — a lesson for anyone building repo classifiers. The primary axis (86 repos) is full-population human-annotated with a 2-pass re-verification protocol. Honest disclosure in t